The structure of the ICPC and the concepts
ICPC is based on a simple bi-axial structure: 17 chapters on one axis, each with an alpha code, and seven identical components with rubrics bearing a two-digit numeric code as the second axis (Figure 1 and Table 2). ICPC has a significant mnemonic quality which facilitates its day-to-day use by physicians, and simplifies the centralized manual coding of data recorded elsewhere.
Each rubric has a three digit code number, a title of limited length, and the codes of the corresponding ICD-10 rubrics. Most rubrics also have inclusion terms, exclusion terms, and “consider” terms.
While ICPC is comprehensive enough to allow classification of the main elements of primary care, it still has some limitations. The rubrics in components 2 to 6 covering the process of care are very broad and non-specific. A classification of medications and drugs was developed for and is described in the report of the European study, but is not yet formally included. ICPC does not include objective findings found during physical examination or investigations. These are all matters for further development.
Residual rubrics (“rag-bags”) are found at the end of a section or subsection; their description includes the word “other”. Clearly, not otherwise specified (NOS) is implied for all of the terms in these rubrics. A knowledge of the boundaries of each section or subsection is required for the best use of the classification. If in doubt, consult the alphabetical index.
The practical use of morbidity/diagnostic data
Until recently classifications were mainly used for the collection of data for health statistics and formulation of policy. The advent of computer based medical records has led to even more widespread use as a means of organizing and storing data gathered during routine clinical encounters. This data is needed, both as part of the patient medical record, and for extraction for health statistics. The classification and coding requirements for those two purposes differ; patient medical records require as much specific detail as possible, whereas health statistics require data which is systematically aggregated into categories based on their frequency or their importance for policy. ICPC was developed for the latter purpose, and must be modified for coding clinical data in medical records.
Optional hierarchical expansion
Clearly, no single international classification can fulfill every need for every user; inevitably users will sometimes want to separate certain problems contained in a single rubric. This usually requires expanded codes using the principle of optional hierarchy. A great deal of expansion is usually needed for coding clinical data in medical records. It is recommended that whenever possible such expansions conform to the usage in ICD-10, or that ICD-10 codes are used as expansion codes, so that maximum comparability between data systems is maintained. Even then provision for including patient specific text is needed for adequate specificity for patient care records.
Episode of care a central concept of general/family practice
The most important new applications of the use of ICPC are in describing the construct of episodes of care and in computer patient records. The two are closely related, and depend upon the use of ICPC as the ordering principle of patient data gathered in general/family practice and primary care.
The WONCA definition of general/family practice refers to “a physician who provides personal, primary, and continuing comprehensive health care to individuals and families”.This is quite similar to that of primary care in the new Institute of Medicine (IOM) definition: “Primary care is the provision of integrated accessible health care services by clinicians who are accountable for addressing a large majority of personal health care needs, developing a sustained partnership with patients and practising in the context of family and community”.
Episode of care
These definitions have been made operational by choosing the “episode of care” as the appropriate unit of assessment.
Episodes of care are distinguished from episodes of illness or disease in a population. An episode of care is a health problem or disease from its first presentation to a health care provider until the completion of the last encounter for that same health problem or disease (Figure 2).
The original three basic elements of encounters to be coded with ICPC (reason for encounter, health problem and interventions) (Figure 2) have now been expanded into six data entry options (A-F) for computer based patient records (Figure 4). The reason for encounter is recorded in two sections: the patient’s symptoms and complaints, and the patient’s requests for interventions. The clinical findings elicited by the physician in the form of symptoms and complaints are coded in addition to those presented as reasons for encounter. Interventions or processes of care are recorded as immediate (those occurring during the encounter) or subsequent (those which will be done subsequently). Work with these, particularly in The Netherlands, has confirmed the usefullness of the concept of reason for encounter, and further refined the concepts of reason for encounter, health problem/diagnosis, and process of care.
Recording systems should be able to distinguish between diagnostic and therapeutic interventions during the encounter (“immediate”, Figure 4 E) and those that will follow (“subsequent”, Figure 4 F). The difference between what is in fact being done by the family doctor at the time of the encounter and what is expected to follow is important for the analysis of utilization data, inter-doctor variation and compliance. It also allows better understanding of the shift from prior probabilities in the first encounter of an episode of care to the posterior probabilities during follow-up19. For recording subsequent interventions a more specific process classification than ICPC provides is needed. Development of this is an ongoing activity of the WONCA Classification Committee.
Episode of disease
The period in which a demonstrable health problem exists: from its onset to its resolution or until the patient’s death. Disease episodes often have well-defined stages:
- Stage of pathological onset: pre-symptomatic stage before the first appearance of symptoms and/or signs. The episode of disease has started, and in some cases, screening may reveal it; in that case, it may lead to an episode of care. In this stage, no episode of illness exists.
- Symptomatic stage: the patient may experience an episode of illness and present the symptoms to an FP, thus starting an episode of care;
- Clinically manifest disease: the period from the moment the diagnosis has labelled the episode of care. The disease may regress spontaneously or by treatment, or may be subject to remissions and relapses or progress to a fatal termination. The episode of care ends with the last encounter for that episode of care (because the patient has recovered, died, or hasn’t visited for it, for whatever reason).
Even though the episode of care may have (temporarily) come to an end, the episode of disease and the episode of illness may continue. Depending on many variables (the disease, the patient, the FP, the health care system), later on, the episode of care can be ‘revived’ (even after years).
Episode of illness
An episode of illness experienced by the patient, from onset of symptoms until their resolution or until the patient’s death. A patient may or may not consult an FP, there may or may not follow an episode of care, and there may or may not be an episode of disease.
Reasons for encounter (RFEs) are the agreed statement of the reasons(s) why a patient enters the health care system, representing the demand for care by that person. They may be symptoms or complaints (headache or fear of cancer), known diseases (flu or diabetes), requests for preventive or diagnostic services (a blood pressure check or an ECG), a request for treatment (repeat prescription), to get test results, or administrative (a medical certificate). These reasons are usually related to one or more underlying problems which the doctor formulates at the end of the encounter as the conditions that have been treated, which may or may not be the same as the reason for the encounter.
Reasons for encounter, health problems/diagnoses, and process of care/interventions form the core of an episode of care consisting of one or more encounters, including changes in their relations over time (“transitions”). An episode of care, consequently, refers to all care provided for a discrete health problem or disease in a particular patient . The “large majority of personal health care needs”, the “comprehensiveness”, the degree of “integration”, of “accessibility”, and of “accountability” can be assessed when episodes of care are classified with ICPC in a computer based patient record.
The reason for encounter (RFE) has been established to be a practical source of patient information, also useful for research and education. This is illustrated by epidemiological data from the Dutch Transition project in the form of standard output, following the rules of the glossary. Beginning with the reason for encounter allows the determination of the probabilities of any given health problem at the start or during follow-up of the episode, per standard sex age group.
Thus the top-10 problems related to cough at the start of an episode show clinically important differences between children aged 5-14 and men aged 65-74 (Table 2). The reverse procedure is equally relevant from a clinical point of view: what reasons for encounter were presented at the start and during follow up of a problem in each standard sex age group? This is illustrated for acute bronchitis (Table 3). These tables document the clinical differences in far more detail than has been possible until now.
The use of reasons for encounter to estimate prior probabilities is clearly very useful; it can be even more so if reasons for encounter presented by the patient such as cough, shortness of breath, fever, abnormal sputum or wheezing (Figure 3 A) are distinguished from clinical findings elicited by the physician during history taking (Figure 3 C). ICPC incorporates over 200 symptoms and complaints serving the classification of reasons for encounter and of clinical findings equally well, though it should be noted that it does not yet include a classification of objective findings. Both applications can be included in the encounter and episode structure of a computer-based patient record (Figure 3 A and C). Together they allow a complete calculation of prior probabilities, while the difference between a symptom expressed by the patient as a reason for encounter or elicited by the physician is retained, and the probabilities can be calculated separately if required.
Reasons for encounter in the form of symptoms, complaints or health problems/diagnoses should be distinguished explicitly from those in the form of requests for interventions such as a prescription, an X-ray, a referral, or advice (Figure 3 A and B). Requests for a certain intervention are often followed by this intervention being performed: when patients ask for medication or a blood test, they often receive it.17 Since patients do actively influence the care provided by general practitioners/family doctors it is important to explicitly document this, also to obtain a better understanding of compliance.
The health problem/diagnosis
The health problem/diagnosis is central to the episode of care and gives it its name. Many health problems are in fact medical diagnoses, but many in primary care are other conditions such as fear of disease, symptoms, complaints, disabilites, or need for care such as immunization. ICPC includes all of these. The health problem may be qualified in terms of its status in the encounter, the certainty which the provider assigns to its diagnosis (and its severity= till now not realized). The status of the episode in an encounter can be specified as new to both doctor and patient, new to doctor but previously treated outside the current provider system, or neither in the case of follow-up encounters. A good computer patient record warns the provider when s/he tries to enter a follow-up encounter for an episode that has not yet been established in the database, or whenever a new one is started when an episode with the same title already exists. This is, obviously, vital to ensure the quality of day to day recording. The extent to which the doctor is certain that his diagnosis is correct is another aspect of an episode of care; this can be graded from uncertain to certain, but a standard means of doing this has not yet been adopted. The inclusion criteria for use of rubrics in ICPC-2 will however help to ensure that the label chosen for the episode is used consistently by all providers. Pop up screens can be used to display options at the time of coding in computer based records.
Interventions, the process of care
The specificity of the three digit ICPC process code to classify immediate interventions is limited, but usually adequate. However when drugs are prescribed a drug code is needed. Because of the vast number of medications involved, and the idiosyncracies of national drug availabilities, no internationally suitable code has yet been produced. In Europe an ICPC drug-code which is ATC-compatible has been valuable and may be suitable for wider adoption.
The core of a computer-based patient record is data coded with ICPC which is language independent: this enhances the use of practice records for a comparison of data from different countries, and it supports the development of general/family practice as an internationally well developed profession with a well defined and empirically based frame of reference. The availability of ICPC in nineteen languages and the growing number of translations of ICD-10 accompanied by alphabetical indexes will allow family doctors in many countries to incorporate a detailed language specific thesaurus in their system, at the same time using ICPC to systematically structure their records and the database in a more standardized way.
Rules for components
The following rules for the use of each component will reinforce the description of the components.
Whenever a code is shown preceded by a dash (-), select the chapter code (alpha). Use A when no specific chapter can be selected, or when multiple chapters are involved. All codes must begin with an alpha code to be complete.
- Biopsy will be coded -52, for digestive system D52, for skin S52.
- Medication prescribed will be coded as -50. A patient requesting medication for asthma R50.
Rubrics from more than one component, or more than one rubric from the same component, can be used for the same encounter if more than one reason is presented by the patient.
- “I’ve had abdominal pain since last night and I vomited several times” D01, D10.
- “I have some abdominal pain and I think that I may have appendicitis” D06, D88.